I have come across one of the 'old school' style 80% receivers but don't have any way to finish the buffer tube hole and threads. I remember the old days when these tools were much more common, but with the new 80% receivers the buffer tubes now come pre-finished.

Is there anyone who might be willing to loan me the BFD (1 1/8" demming drill) and 1 3/16"-16 tpi tap. I'd of course pay for postage each way, and would be happy to throw in either some of my woodworking plans CD-roms or Famous Generals DVD movies or USMC Markmanship Training films DVD (includes Iphone & Ipod format versions, also has all the operators manuals & armorers guides too as PDFs on the same disc).

I'd bore and single-point thread that AR frame in a lathe. A 4-jaw chuck should hold it (backwards) by the buffer tube fitting. Use a long reach drill bit to start the pilot hole then bore it to proper minor thread diameter with a boring bar... a long and rigid boring bar. Then single point that aluminum thing with a long reach threading bar being careful not to allow the rotating receiver front to hit the saddle or toolpost all the while.

This assumes a lathe and single point threading skills.

One other method is to use a lathe to make a special tap in a decent piece of steel. Perhaps a piece of old rifle barrel can provide the steel. I doubt that any heat treat would be needed for one or two uses in 7075T6 aluminum. I'd still bore that minor diameter hole on a lathe as above or with a micrometer boring head in a mill.

VD

05-01-2011, 07:35 AM

tanvil

You will also need the #42 aircraft extention bit.

05-01-2011, 09:07 AM

willie

I have gotten lucky with some large & oddball taps on flea bay just takes tenacity and fortitude waiting. Could take a week or five years.

05-01-2011, 04:21 PM

tanvil

pm sent

05-01-2011, 10:23 PM

Rocster

Yeah...those taps are pricey. I have had a watch alert on eBay now for 5 months on 1 3/16 taps and they never go cheap, I have tried.

And, my first choice was to have a friend help me on his lathe, but he's out of town for a few weeks for a job.

His fixtures are well done- I've done several 80% lowers with them. Exellent results.

05-06-2011, 08:49 PM

tanvil

I agree. You can also raise the back of your lower a tiny bit in the jig and drill the rear take down pin hole slightly low. This will give you a very tight fit with any upper that you decide to use. No slop at all.

05-13-2011, 04:26 AM

Viper Dude

Hello Rocster,
Were you able to solve the tap problem ??? Still looking ???

Check on a large industrial surplus machine tool outlet such as Kitts Industrial Tools in Detroit. Phone: 1-800-521-6579 . (no website). I enjoyed shopping there 30 years ago when living in Michigan.